What is the most critical engine parameter during start?

The most critical engine parameter during start is Turbine Inlet Temperature (TIT). During the engine starting process, monitoring TIT is essential because it directly reflects the thermal limits of the engine. High temperatures at the turbine inlet can indicate potential over-temp conditions, which can lead to engine damage if not managed properly.

As the engine starts, there’s a risk of not achieving proper combustion or experiencing a hot start, which occurs if the engine exceeds its specified TIT limits before the engine has stabilized. Maintaining the TIT within acceptable limits prevents damage to turbine components and ensures that the engine starts safely and effectively.

While other factors like engine RPM, fuel flow rate, and oil pressure are significant during the starting phase, they do not carry the same immediate risk to engine integrity as TIT. Engine RPM gives an indication of engine speed, fuel flow rate influences how much fuel is being introduced for combustion, and oil pressure is important for lubrication, but the turbine inlet temperature is the parameter that must be controlled to prevent catastrophic failure during the start sequence.